The present invention relates to a method of and an apparatus for recording information using an information recording-medium capable of recording information by radiation of an energy beam, or in particular to a method of recording information high in compatibility and accuracy.
A DVD-RAM for realizing a memory capacity of 2.6 GB on one side of a disk 120 mm in diameter using a phase-change material finds practical applications. In forming a recording mark on this disk, the power of an energy beam is changed between high and low levels while the portions (space portions) of the medium between recording marks are irradiated with an energy beam of a predetermined different power level. Specifically, a multi-pulse energy beam is radiated for forming a recording mark and includes (except for short recording marks) four types of pulses, i.e. a first pulse, a multi-pulse chain (middle pulse chain), a last pulse and a negative pulse following the last pulse. This recording method has the advantage that what is called the overwriting (rewriting by overwriting) is possible in which new information is recorded while erasing the existing information. The power level of the energy beam is recorded beforehand in the control data of the recording medium, and the actual radiation power of the energy beam is determined based on this information.
In the prior art described above, the energy amount contained in the middle pulse chain depends on not only the high and low power levels of the middle pulse chain but also the duty factor of the middle pulse chain. Therefore, the energy amount contained in the middle pulse chain cannot be fully controlled simply by setting the high and lower power levels of the middle pulse chain to a predetermined value. For this reason, a recording mark is not necessarily formed to the correct shape by the middle pulse chain, often deteriorating the compatibility of recording. Especially in the case where information is recorded with high density in a 4.7 GB DVD-RAM, an insufficient energy amount in the middle portion of the recording mark under unstable control forms a recording mark with a thin middle portion, or an insufficient magnitude of the rear portion of the recording mark, thereby causing an unrequired edge shift in the reproduction signal and thus an insufficient compatibility for recording and reproduction. An excessively large energy amount resulting from an unstable control of the middle portion of the recording mark, on the other hand, forms a recording mark with a thick middle portion or with an excessively large rear portion, and generates an unrequired edge shift in the reproduction signal, thereby leading to the problem of an insufficient compatibility for recording and reproduction.
According to one aspect of the invention, there is provided a method of recording information for forming each recording mark in a recording medium by radiating a pulse chain of an energy beam including a first pulse, a middle pulse chain, a last pulse and a negative pulse following the last pulse, comprising the steps of:
recording the designated values of the power level of the first pulse, the upper and lower power levels of the middle pulse chain, the power level of the last pulse and the power level of the negative pulse in a control data zone of the recording medium in advance;
adjusting the average power of the first pulse to the designated power level value of the first pulse in the control data zone;
adjusting the average power of the middle pulse chain to the arithmetic mean of the designated upper power level value and the designated lower power level value in the control data zone;
adjusting the average power of the last pulse to the designated power level of the last pulse in the control data zone;
adjusting the average power of the negative pulse to the designated power level of the negative pulse in the control data zone; and
adjusting the variation of the power level of the energy beam of the middle pulse chain to the difference between the designated upper power level and the designated lower power level in the control data zone.
According to another aspect of the invention, there is provided an apparatus for controlling the ratio of the average power between the first pulse, the middle pulse chain and the last pulse to a predetermined value.